Cover latch mechanism

ABSTRACT

Latching apparatus for retaining a cover in extremely tight engagement with a housing at all points of the cover perimeter, as for a cabinet sealed against radio frequency interference. The apparatus comprises a series of latches spaced about the cover perimeter, each latch including a flat-end bolt on the cover which slides behind a cylindrical strike on the housing. A cable which extends over pulleys and along the perimeter of the cover operates each latch, and a hand or power operated lever moves the cable to operate all latches simultaneously.

United States Patent [72] Inventor Leo J. Emenaker L08 Angeles, Calit. 21 Appl. NO. 749,143 [22] Filed July 31, 1968 [45] Patented June 15, 1971 [73] Assignee Data Products Corporation Culver City, Calif.

[54] COVER LATCH MECHANISM 3 Claims, 7 Drawing Figs.

[52] 1.1.8. 292/38, 292/2 [51] lnt.Cl 1505c 9/16 [50] Field of Search 292/2, 9, 34, 36, 28, 38, 39, 40, 50,141, 341.11, 341.12, 341.13; 339/91 [56] References Cited UNITED STATES PATENTS 522,103 6/1894 Burton 109/61 964,265 7/1910 Johnson 292/33 2,100,591 11/1937 Haberstump 292/302 2,331,403 10 1943 Leonard 292/34 1.15

928,904 7/1909 com-611 70/71 1,006,211 10/1911 Herman.... 292/36 2,879,725 3/1959 Zuver 109/39 2,910,857 11/1959 141165561 70/92 2,996,322 8/1961 McClellan... 292/36 3,072,286 1/1963 Cusumano 220/46 FOREIGN PATENTS 163,817 11/1933 Switzerland 292/341.11 561,248 10/1932 Germany 292/341.11

Primary ExaminerMarvin A. Champion Assistant Examiner-Robert L. Wolfe Attorneys-Samuel Lindenberg and Arthur Freilich ABSTRACT: Latching apparatus for retaining a cover in extremely tight engagement with a housing at all points of the cover perimeter, as for a cabinet sealed against radio frequency interference. The apparatus comprises a series of latches spaced about the cover perimeter, each latch including a flatend bolt on the cover which slides behind a cylindrical strike on the housing. A cable which extends over pulleys and along the perimeter of the cover operates each latch, and a hand or power operated lever moves the cable to operate all latches simultaneously.

COVER LATCH MECHANISM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to cover closing mechanisms.

2. Description of the Prior Art Electronic apparatus which is sensitive to radiofrequency interference is often installed in housings which are sealed against electromagnetic radiation. Such sealing is realized by utilizing a housing of good electrical conductivity and by installing strips of conductive material along joints or other places where cracks might exist through which radiation might leak in or out. It is found that such strips must be pressed tightly in place along their entire length to effect good electrically conductive sealing, as by providing many holding screws which are spaced at close intervals.

In designing such radiationtight housings, it is often desirable to provide large covers which can be readily opened and closed, to permit ready access to the electronic apparatus. A strip of conductive material mounted along the perimeter of the cover can be used to seal it to the housing, but only if the cover is pressed closed at many places around its perimeter. Otherwise, some portions of the cover do not press the sealing strip hard enough and radiation can leak through. While a series of many Iatchescan be used, the annoyance in separately operating many latches makes the cover inconvenient to open and close.

The opening and closing of a radiationtight cover would be facilitated by mechanisms which enabled all of the latches around the cover perimeter to be operated simultaneously by moving a single handle or the like. However, the pressing force required to effect reliable sealing with presently available sealing strips is on the order of pounds per linear inch of seal. Thus, a cover measuring 3 feet by 3 feet would have to be pressed in with a total force of approximately 1,400 pounds. The latches available heretofore required large amounts of force to operate, and not enough force could be exerted by one man to readily operate all latches at one time. This difficulty was compounded by over center type mechanisms which required considerably more than the final closing force to operate the latch to the closed state. In addition, no apparatus for simultaneously operating the latches was available which was simple and economical.

Thus, apparatus which facilitated the closing of a cover in extremely tight engagement with a housing would facilitate the use of radiation sealed enclosures. Such apparatus would prove useful in a variety of other applications where a cover had to be tightly closed at many points along its perimeter.

OBJECTS AND SUMMARY OF THE INVENTION One object of the present invention is to provide apparatus for rapidly closing a cover tightly on a housing.

Another object is to provide a latch mechanism which enables high closing pressures to be applied using only relatively small latch-operating forces.

In accordance with the present invention, latching apparatus is provided which enables a cover to be closed in tight engagement with a housing around the entire perimeter of the cover. The apparatus comprises a group of latches spaced around the cover perimeter. A linking member such as a cable or other tension member extends along the perimeter of the cover and is coupled to each of the latches to operate them. A handle mounted on the cover enables the cable to be pulled to operate all of the latches simultaneously.

In one embodiment of the invention, each latch mechanism comprises a strike fixed to the housing, and a bolt mounted on the cover for sliding behind the strike to close the cover. A lever mounted on the cover has one end engaged with the bolt and the other end'engaged with the cable. When the cable moves in one direction, the lever pivots to slide out the bolt to engage the strike, and when the cable moves in the other direction, the lever pivots back to return the bolt.

For a rectangular cover constructed in accordance with the foregoing embodiment, four pulleys are mounted at the four corners of the cover. The cable extends around the four pulleys, so it lies along the four sides of the cover. Generally one or more latches are positioned along each side of the cover. The bolt-operating lever of each latch is connected to the cable. A handle is mounted on the cover for pulling the cable in either direction, so that a half-turn of the handle operates all latches simultaneously.

The strike is of cylindrical shape, and the surface of the bolt which lies behind the strike is flat. As the bolt engages the strike and closing progresses, the force applied to slide the bolt out results in a much greater force pushing the bolt behind the strike. This allows a very large closing force to be applied to the cover, such as thousands of pounds, by a cable tension on the order of a hundred pounds. As a result, a relatively light cable and pulley systemcan be used. The cable tension is applied by a force of tens of pounds applied at the end of the cable-operating handle.

The novel features of the invention are set forth with particularity in the appended claims. The invention will best be understood from the following description when read in conjunction with the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of cover latching apparatus constructed in accordance with the invention, with the cover shown opened on a housing;

FIG. 2 is a perspective view of the cable pulling block of the latching apparatus of FIG. 1;

FIG. 3 is a partial perspective view of the cover and housing of FIG. 1, showing the cover hinge portion thereof;

FIG. 4 is a partial sectional view taken on the line 4-4 of FIG. 1;

FIG. 5 is a partial sectional view taken on the line 5-5 of FIG. 4;

FIG. 6 is a partial view showing the bolt and strike of the latching apparatus of FIG. 1; and FIG. 7 is a partial view of a bolt and strike constructed in accordance with another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS "As shown in FIG. 1, the apparatus comprises a cover 10 which is closed over an opening 12 in a housing 14. The housing 14 is designed to hold sensitive electronic equipment, such as a high-speed line printer, which must be shielded against radiofrequency interference (RF I). The housing is constructed of metal so it is electrically conductive and therefore prevents the passage of RFI. Similarly, the cover 10 has a frame 16 and panel 18 of metal to prevent the passage of RFI therethrough. However, RFI can leak through even small cracks which might exist between the cover and housing even when the cover is closed tightly on the housing.

To prevent RFI leakage through any crack between the cover 10 and housing 14, a sealing strip 20 is provided which is constructed of electrically conductive material. A typical sealing strip comprises multiple layers of metal screen molded in a matrix of rubber and particles of copper or silver. In order to assure reliable sealing against RFI, a typical sealing strip which is approximately one-fourth inch in width must be pressed between the cover and housing by a force of approximately 10 pounds per linear inch of the strip. A cover 10 of reasonable weight is not rigid enough to distribute the required force uniformly along its perimeter if held closed at only two points, so a group of latches is provided which are spaced along the cover perimeter. In the'cover of FIG. 1, eight latches are pro vided, with two positioned on each side of the cover.

Each latch comprises a pair of latch engaging means mounted on the cover and housing, respectively, which can be engaged with each other to hold one portion of the cover closed. For example, the latch shown at 22 comprises a strike assembly 24 mounted on the front plate 26 of the housing, and

a bolt assembly 28 mounted on the frame of the cover. The bolt assembly includes a bolt 30 which can be slid behind a strike 32 of the strike assembly to hold the cover closed. The bolt 30 is moved by a lever 34 which is engaged by a lever operating block 36 fixed to a cable 38. When the block 36 moves down, the lever is pivoted to retract the bolt from the strike, and vice versa. Seven other blocks which are fixed to the cable 38 operate the levers of the other seven latches in the same manner.

The cable 38 which operates all of the latches, extends along the perimeter of the cover at all four sides thereof. Four pulleys 40 rotatably mounted at the corners of the cover, guide the cable along the perimeter of the cover. The ends of the cables are tied together by a cable pulling block 42, to form a continuous loop of cable. The block 42 has turnbuckle members 41 that hold the cable taut. The cable pulling block 42 can be moved in the direction of the arrow 44 to move the cable in a direction that closes all the latches, or in the opposite direction to open the latches. An operating lever 46 for receiving forces that operate the latches, is pivotally mounted on the cover frame to enable hand operation of the apparatus. If desired, the latching mechanism can be motor operated. As shown in FIG. 2, the operating lever 46 has a crankpin 48 mounted off the center of the lever pivot, that engages a hole 51 in the cable pulling block. Rotation of the operating lever to position 46A moves the crankpin, which in turn moves the cable pulling block. Rotation of the operating lever back toward its original position causes the crankpin to move the cable pulling block back to its original position.

FIG. 3 illustrates one of two hinges which hold the cover 10 when it is swung open. The hinge 52 comprises a hinge pin 54 fixed to a hinge mount 56 on the housing and engaged in a hinge bearing hole 58 on the cover frame. The bearing hole 58 in which the hinge pin pivots is not round, but is elongated. This allows the cover to move a slight distance toward the housing when the latches are engaged, without interference from the hinge pin 54. Thus, the hinge 52 does not serve to keep the cover closed tightly, as is the case in most ordinary covers, but merely to support the cover when it is swung open.

FIGS. 4 and show the details of the latch 22, in the configuration wherein the cover is tightly closed to press the sealing strip against the front plate 26 of the housing. The bolt 30 slides within a pair of bearing holes 60 and 62 formed in the cover frame 16. The bolt is cylindrical, but has a flat cutaway end portion 64 where it is engaged with the strike 32. The strike 32 is a cylindrical shaft pivotally mounted between a pair of legs 61 and 63 of a strikesupport 65. The strike support is bolted to the front plate 26 of the housing.

The bolt is slid in and out by operating the lever 34, which is pivoted at 66 on the cover frame. The lever includes two spaced plates joined at the side 68 of the lever, the lever generally being formed by bending a single plate in half. The lever has a rounded bolt-engaging end 70, which is engaged in a pair of notches 72 and 74 formed on either side of the bolt. The opposite end of the lever is a cable-operated end 76, which engages the lever operating block 36 that is mounted on the cable 38 The block includes two halves which are held tight on the cable by a pair of screws 78. One end of the block 36 has a pair of notches 80 on either side for receiving the rounded cable engaging end 76 of the lever.

The cover 10 is closed tightly on the housing by swinging it shut and then turning the operating handle 46. This moves the cable 38 along the direction of its length, and moves the blocks 36 attached to the cable. The blocks move the cableoperated ends 76 of the levers, causing the levers to pivot. As the levers pivot, the bolt-engaging ends 70 move the bolts 30 toward the strikes 32 on the housing. The bolt 30 and strike 32 are positioned so that the flat-end portion 64 of the bolt lies behind the strike only when the RFI sealing strip has been compressed to the required thickness. When all eight bolts are fully engaged with the strike, the cover 10 is firmly held against forces applied in any direction, and it resists high levels of vibration and shock.

FIG. 6 is an enlarged view of the bolt 30 and strike 32, illustrating the forces employed in effecting closure. The bolt position shown at 30 in the figure is the position at which the RF l sealing strip first begins to be compressed. Therefore, this position 30 is also the position at which the bolt first engages the strike, at the portion 86 of the strike which has a surface component facing the bolt. The engaging tip 82 of the bolt lies at a distance in back of the center of the strike which is approximately one-half the radius R of the strike. Accordingly, if a force F is applied to the bolt to slide it toward the strike, this gives rise to a closing force G tending to move the bolt behind the strike, where G is approximately 58 percent of F.

As the bolt 30 is slid further toward the strike, the closing force which presses the cover against the housing, increases even for a constant bolt-sliding force. At the bolt position 30A, the tip 82A of the bolt lies at a distance of nine-tenths R behind the center of the strike. At this position, the bolt-sliding force Fa gives rise to a closing force Ga which is approximately 2.1 times as great as Fa. Thus, as the RFI sealing strip is compressed, and a constantly increasing closing force must be applied to press the cover against the housing, the required bolt-sliding force does not increase proportionately. In fact, in many instances the bolt-sliding force is substantially constant between the initial engagement with the strike portion 86 when the bolt is at position 30 and nearly total closure at position 30A, and it decreases after the position 30A is reached. When the portion 88 on the strike which faces the housing, is reached by the bolt, only enough sliding force on the bolt is required to overcome friction.

The limited bolt-sliding force allows the use of relatively light duty levers 34 and a small diameter cable 38 to transmit the closing forces. Only the strike 32, bolt 30, and bearing holes 60 and 62 within which the bolts move must withstand large forces, and the latching apparatus can be manufactured economically. In closing the latch, the maximum closing force tending to press the cover toward the housing is reached when the cover is fully closed. This is unlike many latch mechanisms wherein a closing force which is substantially greater than the final closing force is applied, to prevent the latch from springing open.

While the rotatably mounted strike 32 of cylindrical shape can be used, a stationary strike of a shape other than cylindrical can also be used. However, it is preferable that the strike have a convexly rounded surface between the portion facing the housing shown at 88 and an area where the bolt first engages the strike, as at position 86 on the strike. A convexly rounded surface, such as a cylindrical surface, increases the multiplication of the sliding force in effecting closure. A rotatably mounted strike has an important advantage in reducing friction as it rolls on the bolt.

FIG. 7 illustrates another embodiment of the invention, wherein the end portion 648 of the bolt 30B is formed so that a line 83 parallel to the flat surface thereof makes a small angle P with a line 84 which is parallel to the direction in which the bolt slides. The angle P is in a direction to provide an angle of more than 90 between the direction of bolt sliding during movement of the bolt towards the strike and a line 85 normal to the surface at the end of the bolt. This helps to assure that the bolt will not slide back accidentally when subjected to vibrations. However, the angle P is only on the order of several degrees, e.g., about 5, so that the bolt still extends substantially parallel to the direction in which it slides. As a result, a maximum closing force and compression of the RFI sealing strip is reached which is only slightly greater than the final closing force and sealing strip compression.

Another manner of assuring that the bolts will not be withdrawn is to mount the operating lever 46, shown in detail in FIG. 2, so that it can rotate a small amount, such as 10, past the maximum closed position. It is found that appreciable cable tension or bias remains which tends to withdraw the bolts from the strikes when the latches are fully closed. The placement of a stop 47 for the lever 46 to permit lever movement slightly past the closed position causes remaining cable bias to tend to retain the latches closed.

The latching mechanisms can be mounted in a number of ways. For example, the cable and bolt assemblies can be mounted on the housing, while the strikes are mounted on the cover. Other means than cables can be used to transmit the tension forces which operate the latches, such as long rods, chains, belts, and so forth. However, the cable and pulley supports generally provide greater simplicity and lower cost. The ability to apply high closing forces at many points around the cover can be utilized in a number of other closing situations, and therefore the latching apparatus is useful in a variety of applications.

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and, consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

What I claim is:

1. Apparatus for tightly sealing a cover element about an opening in a housing element comprising:

sealing means disposed on one of said elements and extending about said opening, said sealing means being compressible between said elements when they are closed on each other to form a seal between them; and

a plurality of latches disposed about said opening, each latch including a strike mounted on a first of said elements, a bolt slidably mounted on a second of said elements, and means for sliding said bolt toward and away from said strike; and wherein each of said strikes is substantially cylindrical and each of said bolts has a substantially flat strike-engaging surface for movement behind said strike, each of said bolts being mounted for slidable movement in a direction substantially parallel to its flat strike-engaging surface; and

each of said bolts has a strike-engaging tip mounted to contact said strike at a location behind the axis of said cylindrical strike but substantially in front of the rearmost portion of said strike when said cover is pressed closed but before full compression of said sealing strip.

2. Apparatus for tightly sealing a cover element about an opening in a housing element comprising:

sealing means disposed on one of said elements and extending about said opening, said sealing means being compressible between said elements when they are closed on each other to form a seal between them; and

a plurality of latches disposed about said opening, each latch including a strike mounted on a first of said elements, a bolt slidably mounted on a second of said elements, and means for sliding said bolt toward and away from said strike; and wherein at least a portion of each of said strikes is substantially cylindrical, and each of said bolts has a tip mounted to engage said strike a distance spaced behind the axis of said cylindrical portion by on the order of one-half the radius of said cylindrical portion, when said cover is closed to a position where said sealing means first begins to be substantially compressed.

3. The apparatus described in claim 2 wherein:

said bolt has a flat portion for movement behind said strike, said tip being located substantially at one end of said flat portion, and said bolt is slidably mounted so that it slides in a direction substantially parallel to said flat portion. 

1. Apparatus for tightly sealing a cover element about an opening in a housing element comprising: sealing means disposed on one of said elements and extending about said opening, said sealing means being compressible between said elements when they are closed on each other to form a seal between them; and a plurality of latches disposed about said opening, each latch including a strike mounted on a first of said elements, a bolt slidably mounted on a second of said elements, and means for sliding said bolt toward and away from said strike; and wherein each of said strikes is substantially cylindrical and each of said bolts has a substanTially flat strike-engaging surface for movement behind said strike, each of said bolts being mounted for slidable movement in a direction substantially parallel to its flat strike-engaging surface; and each of said bolts has a strike-engaging tip mounted to contact said strike at a location behind the axis of said cylindrical strike but substantially in front of the rearmost portion of said strike when said cover is pressed closed but before full compression of said sealing strip.
 2. Apparatus for tightly sealing a cover element about an opening in a housing element comprising: sealing means disposed on one of said elements and extending about said opening, said sealing means being compressible between said elements when they are closed on each other to form a seal between them; and a plurality of latches disposed about said opening, each latch including a strike mounted on a first of said elements, a bolt slidably mounted on a second of said elements, and means for sliding said bolt toward and away from said strike; and wherein at least a portion of each of said strikes is substantially cylindrical, and each of said bolts has a tip mounted to engage said strike a distance spaced behind the axis of said cylindrical portion by on the order of one-half the radius of said cylindrical portion, when said cover is closed to a position where said sealing means first begins to be substantially compressed.
 3. The apparatus described in claim 2 wherein: said bolt has a flat portion for movement behind said strike, said tip being located substantially at one end of said flat portion, and said bolt is slidably mounted so that it slides in a direction substantially parallel to said flat portion. 